//CircleSegment.java
//calculate segment, sector, chord etc of circle

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.border.*;
import java.util.*;
import java.text.*;

public class CircleSegment extends JApplet implements ActionListener {     

    double r, a, rad, c, h,  arc, sectorArea, triangleArea, segmentArea;
    JPanel controlPanel;
    JLabel rLabel, aLabel, radLabel, cLabel, arcLabel, hLabel, sectorAreaLabel,triangleAreaLabel,segmentAreaLabel;
    JTextField rTextField, aTextField, radTextField, cTextField, arcTextField, hTextField,
    	sectorAreaTextField, triangleAreaTextField, segmentAreaTextField;
    int endX, endY;  //so mouseListener has access
    int rLen;
    int midX, midY;
	//int midY = h/2;
    DecimalFormat d4, i1;
    
    public void init() {
	String input;
	d4 = new DecimalFormat ("0.0000");
	i1 = new DecimalFormat ("0.000");
	
	Container container = getContentPane();
	container.setLayout( new BorderLayout() ); 

	controlPanel = new JPanel();
	controlPanel.setLayout(new FlowLayout());
	controlPanel.setBackground(Color.MAGENTA);
	controlPanel.setBorder(BorderFactory.createEtchedBorder(EtchedBorder.RAISED));
	container.add(controlPanel,BorderLayout.NORTH);

	aLabel = new JLabel( "ANGLE \u03B1\u00B0" );
	controlPanel.add( aLabel );
	aTextField = new JTextField("90.0",4);
	a = Double.parseDouble(aTextField.getText());
	aTextField.setHorizontalAlignment(JTextField.RIGHT);
	aTextField.addActionListener( this );
	controlPanel.add( aTextField );
	
	radLabel = new JLabel( "rad" );
	controlPanel.add( radLabel );
	rad = Math.toRadians(a);
	radTextField = new JTextField(""+d4.format(rad),4);   
	radTextField.setHorizontalAlignment(JTextField.RIGHT);
	radTextField.addActionListener( this );
	controlPanel.add( radTextField );
 			
	rLabel = new JLabel( "  LENGTHS: radius" );
	controlPanel.add( rLabel );
	rTextField = new JTextField("1.0",4);
	r = Double.parseDouble(rTextField.getText());
	rTextField.setBackground(new Color(200,200,255));
	//rTextField.setForeground(Color.WHITE);
	rTextField.setHorizontalAlignment(JTextField.RIGHT);
	rTextField.addActionListener( this );
	controlPanel.add( rTextField );
	
	cLabel = new JLabel( "chord" );
	controlPanel.add( cLabel );
	c = chordLength(r,a);
	cTextField = new JTextField(""+d4.format(c),4);
	cTextField.setBackground(Color.CYAN);
	cTextField.setHorizontalAlignment(JTextField.RIGHT);
	cTextField.addActionListener( this );
	controlPanel.add( cTextField );

	hLabel = new JLabel( "h" );
	controlPanel.add( hLabel );
	h = heightLength(r,c);
	hTextField = new JTextField(""+d4.format(h),4);
	hTextField.setBackground(Color.YELLOW);
	hTextField.setHorizontalAlignment(JTextField.RIGHT);
	hTextField.addActionListener( this );
	controlPanel.add( hTextField );

	arcLabel = new JLabel( "arc" );
	controlPanel.add( arcLabel );
	arc = arcLength(r,a);
	arcTextField = new JTextField(""+d4.format(arc),4);
	arcTextField.setBackground(Color.PINK);
	arcTextField.setHorizontalAlignment(JTextField.RIGHT);
	arcTextField.addActionListener( this );
	controlPanel.add( arcTextField );

	sectorAreaLabel = new JLabel( "  AREAS: sector" );
	controlPanel.add( sectorAreaLabel );
	sectorArea = sectorArea(r,a);
	sectorAreaTextField = new JTextField(""+d4.format(sectorArea),4);
	sectorAreaTextField.setBackground(Color.PINK);
	//sectorAreaTextField.setForeground(Color.WHITE);
	sectorAreaTextField.setHorizontalAlignment(JTextField.RIGHT);
	sectorAreaTextField.addActionListener( this );
	controlPanel.add( sectorAreaTextField );	
		
	triangleAreaLabel = new JLabel( "- triangle" );
	controlPanel.add( triangleAreaLabel );
	triangleArea = triangleArea(r,a);
	triangleAreaTextField = new JTextField(""+d4.format(triangleArea),4);
	triangleAreaTextField.setBackground(Color.PINK);
	triangleAreaTextField.setHorizontalAlignment(JTextField.RIGHT);
	triangleAreaTextField.addActionListener( this );
	controlPanel.add( triangleAreaTextField );	
		
	segmentAreaLabel = new JLabel( "= segment" );
	controlPanel.add( segmentAreaLabel );
	segmentArea = sectorArea - triangleArea;
	segmentAreaTextField = new JTextField(""+d4.format(segmentArea),4);
	segmentAreaTextField.setBackground(Color.PINK);
	segmentAreaTextField.setHorizontalAlignment(JTextField.RIGHT);
	//segmentAreaTextField.setEditable(false);
	segmentAreaTextField.addActionListener( this );
	controlPanel.add( segmentAreaTextField );			
	
	rLen = getHeight()/3;  //mouseListener needs
	midX = getWidth()/2;
	midY = getHeight()/2;
		
	
	rTextField.setText("1.0");
	rTextField.postActionEvent();  //fires listener
	
  	//incantation that responds to mouse move events:
	addMouseMotionListener(
	       new MouseMotionAdapter() {
		   public void mouseDragged( MouseEvent event) {
	               int px = event.getX();
	               int py = event.getY();
	               double x=-999, y=-999;  //inits to fake out compiler for showStatus
	               
		       double mouseDistance = distanceFormula(px,py, endX,endY);
		       
		       if (mouseDistance < 50) { //within 50 of endPoint
		           if (a < 180) {  //left right: px change
	               	       /*if (px < endX)   //leftward
	               	           //scale px to actual x, then a=acos(x/r)
	               	           x = (double)endX/rLen - (double)px/rLen;
	               	       else
	               	       	   x = (double)px/rLen - (double)endX/rLen;
	               	       	   */
	               	       x = (double)(px-midX)/rLen;
	               	       if (x <= r && x >= -r)   //avoid going under?? at 0
	               	           a = Math.toDegrees(Math.acos(x/r));
	               	       //if (a < 0)  // ?? nope
	               	       	 //  a = 0;
		           }
		           else if (a > 180) {  //left right: opp. of upper half circle
	               	       x = (double)(midX-px)/rLen;
	               	       if (x <= r && x >= -r)   //avoid going under?? at 360
	               	           a = 180 + Math.toDegrees(Math.acos(x/r));
		               
		           }
		           else { //a==180  ??
		               if (py != midY) {  //has to be at least one pixel above or below
		                   y = (double)(py-midY)/rLen;
		                   a = 180 + Math.toDegrees(Math.asin(y/r));
		               }
		           }
	               	   //showStatus("("+px+","+(getHeight()-py)+")  x="+x+"  y="+y+"  a="+a);
		           aTextField.setText(""+i1.format(a));
	                   aTextField.postActionEvent(); 
		       }   	
		   } 
	       }
	 );    
   }


    public void setTextFields(double a, double rad, double r, double c, double h, double arc,
   			     double sectorArea, double triangleArea, double segmentArea) {
       aTextField.setText(""+i1.format(a));   			    	
       radTextField.setText(""+d4.format(rad));   			    	
       rTextField.setText(""+d4.format(r));   	
       cTextField.setText(""+d4.format(c));
       hTextField.setText(""+d4.format(h));
       arcTextField.setText(""+d4.format(arc));
       sectorAreaTextField.setText(""+d4.format(sectorArea));
       triangleAreaTextField.setText(""+d4.format(triangleArea));
       segmentAreaTextField.setText(""+d4.format(segmentArea));
    }

    public void actionPerformed( ActionEvent event ) {
    	try {
	    double aTry = Double.parseDouble(aTextField.getText());
	    if (aTry<0 || aTry>360) {
	      	JOptionPane.showMessageDialog(null,
					  "angle must be between 0 and 360 degrees",
					  "CircleSegment: Invalid ANGLE DEGREES input",
					  JOptionPane.ERROR_MESSAGE);
	        return;
	    }
	    double radTry = Double.parseDouble(radTextField.getText());
	    if (radTry<0 || radTry>2*Math.PI+.001) {
	      	JOptionPane.showMessageDialog(null,
					  "angle must be between 0 and 2\u03C0 radians",
					  "CircleSegment: Invalid ANGLE RADIANS input",
					  JOptionPane.ERROR_MESSAGE);
	        return;
	    }
	    double rTry = Double.parseDouble(rTextField.getText());
	    if (rTry<0) {
	      	JOptionPane.showMessageDialog(null,
					  "radius must be greater than 0",
					  "CircleSegment: Invalid RADIUS input",
					  JOptionPane.ERROR_MESSAGE);
	        return;
	    }
	    double cTry = Double.parseDouble(cTextField.getText());
	    if (cTry<0 || cTry>2*r) {
	      	JOptionPane.showMessageDialog(null,
					  "chord length must be between 0 and diameter",
					  "CircleSegment: Invalid CHORD LENGTH input",
					  JOptionPane.ERROR_MESSAGE);
	        return;
	    }
	    double hTry = Double.parseDouble(hTextField.getText());
	    if (hTry<0 || hTry>r) {
	      	JOptionPane.showMessageDialog(null,
					  "height length must be between 0 and radius",
					  "CircleSegment: Invalid HEIGHT input",
					  JOptionPane.ERROR_MESSAGE);
	        return;
	    }
	    double arcTry = Double.parseDouble(arcTextField.getText());
	    if (arcTry<0 || arcTry>2*Math.PI*r +0.001) {
	      	JOptionPane.showMessageDialog(null,
					  "arc length must be between 0 and circumference",
					  "CircleSegment: Invalid ARC LENGTH input",
					  JOptionPane.ERROR_MESSAGE);
	        return;
	    }
	    double sectorTry = Double.parseDouble(sectorAreaTextField.getText());
	    if (sectorTry<0 ||sectorTry>Math.PI*r*r +0.001) {
	      	JOptionPane.showMessageDialog(null,
					  "sector area must be between 0 and circle's area",
					  "CircleSegment: Invalid SECTOR AREA input",
					  JOptionPane.ERROR_MESSAGE);
	        return;
	    }
	    double triangleTry = Double.parseDouble(triangleAreaTextField.getText());
	    if (triangleTry<0 || triangleTry>r*r/2 +0.001) {   // max possible triangle at 90 deg
	      	JOptionPane.showMessageDialog(null,
					  "triangle area must be between 0 and 90\u00B0 max",
					  "CircleSegment: Invalid TRIANGLE AREA input",
					  JOptionPane.ERROR_MESSAGE);
	        return;
	    }
	    double segmentTry = Double.parseDouble(segmentAreaTextField.getText());
	    if (segmentTry<0 || segmentTry>Math.PI*r*r/2 +0.001) {
	      	JOptionPane.showMessageDialog(null,
					  "segment area must be between 0 and semicircle area",
					  "CircleSegment: Invalid SEGMENT AREA input",
					  JOptionPane.ERROR_MESSAGE);
	        return;
	    }
	}
	catch (NumberFormatException e) {
	    JOptionPane.showMessageDialog(null,
					  "all values must be numbers",
					  "CircleSegment: Invalid input",
					  JOptionPane.ERROR_MESSAGE);
	    return;
	}
	
    	if ( event.getSource() == aTextField ) {
	    a = Double.parseDouble(aTextField.getText());
	    rad = Math.toRadians(a);
	    arc = arcLength(r,a);
	    sectorArea = sectorArea(r,a);
	    if (a <= 180) {
	        c = chordLength(r,a);
	        h = heightLength(r,c);
	        triangleArea = triangleArea(r,a);
	        segmentArea = sectorArea - triangleArea;
	        setTextFields(a,rad,r,c,h,arc,sectorArea,triangleArea,segmentArea);
	    }
	    else {
	    	c = 0;
	    	h = 0;
	    	triangleArea = 0;
	    	segmentArea = 0;
	        setTextFields(a,rad,r,c,h,arc,sectorArea,triangleArea,segmentArea);
	    }
	    repaint();    
	}
	else if ( event.getSource() == radTextField ) {
	    rad = Double.parseDouble(radTextField.getText());
	    a = Math.toDegrees(rad);
	    aTextField.setText(""+i1.format(a)); 
	    aTextField.postActionEvent();  //fires its listener
	}
	else if ( event.getSource() == rTextField ) {
	    r = Double.parseDouble(rTextField.getText());
	    c = chordLength(r,a);
	    h = heightLength(r,c);
	    arc = arcLength(r,a);
	    sectorArea = sectorArea(r,a);
	    triangleArea = triangleArea(r,a);
	    segmentArea = sectorArea - triangleArea;
	    setTextFields(a,rad,r,c,h,arc,sectorArea,triangleArea,segmentArea);
	    repaint();    		
	}		
	else if ( event.getSource() == cTextField ) {
	    c = Double.parseDouble(cTextField.getText());
	    a = Math.toDegrees(Math.acos(1-c*c/(2*r*r)));
	    aTextField.setText(""+i1.format(a)); 
	    aTextField.postActionEvent();  //fires its listener
	}
	else if ( event.getSource() == hTextField ) {
	    h = Double.parseDouble(hTextField.getText());
	    a = Math.toDegrees(Math.acos(2*h*h/(r*r)-1));
	    aTextField.setText(""+i1.format(a)); 
	    aTextField.postActionEvent();  //fires its listener
	}
	else if ( event.getSource() == arcTextField ) {
	    arc = Double.parseDouble(arcTextField.getText());
	    a = 180*arc/(Math.PI*r);
	    aTextField.setText(""+i1.format(a)); 
	    aTextField.postActionEvent();  //fires its listener
	}
	else if ( event.getSource() == sectorAreaTextField ) {
	    sectorArea = Double.parseDouble(sectorAreaTextField.getText());
	    a = 360*sectorArea / (Math.PI*r*r);
	    aTextField.setText(""+i1.format(a)); 
	    aTextField.postActionEvent();  //fires its listener
	}
	else if ( event.getSource() == triangleAreaTextField ) {
	    triangleArea = Double.parseDouble(triangleAreaTextField.getText());
	    a = Math.toDegrees(Math.asin(2*triangleArea/(r*r)));
	    aTextField.setText(""+i1.format(a)); 
	    aTextField.postActionEvent();  //fires its listener
	}
	else if ( event.getSource() == segmentAreaTextField ) {
	    /*JOptionPane.showMessageDialog(null,
			"Sorry, not yet implemented!\nReverting to previous value.",
			"CircleSegment: Unimplemented",
			JOptionPane.WARNING_MESSAGE);
            segmentAreaTextField.setText(""+d4.format(segmentArea));
	   */
	    segmentArea = Double.parseDouble(segmentAreaTextField.getText());
	    a = NewtonsAlpha(r,segmentArea);
	    aTextField.setText(""+i1.format(a)); 
	    aTextField.postActionEvent();  //fires its listener
	}		
    }
    
    public void paint (Graphics g) {
	super.paint( g );   //erase 
        g.setFont( new Font( "SansSerif", Font.BOLD, 12 ) );

	g.drawString("Set any parameter ",5,50);
	g.drawString("OR  Drag endpoint of radius around circle",5,70);

	int w = getWidth();
	int h = getHeight();
	//int midX = w/2;
	//int midY = h/2;
	//int rLen = h/3;
	
	//g.drawOval(midX-rLen, midY-rLen, 2*rLen, 2*rLen);
	g.drawArc(midX-rLen,midY-rLen,2*rLen,2*rLen, (int)a,360-(int)a);	
	g.fillRect(midX-1,midY-1, 2,2);
	g.drawString("(0,0)",midX-5,midY+10);
	
	g.setColor(Color.BLUE);
	g.drawLine(midX,midY, midX+rLen ,midY);
	g.drawString("("+r+",0)",midX+rLen+1,midY);

	//int endX, endY;
	endX = (int)(Math.cos(Math.toRadians(a)) * rLen + midX);
	endY = h - (int)(Math.sin(Math.toRadians(a)) * rLen + midY);
	g.drawLine(midX,midY, endX,endY);
	if (a<=90 || a>=270)
	    g.drawString("("+d4.format(Math.cos(Math.toRadians(a))*r)+","+
		         d4.format(Math.sin(Math.toRadians(a))*r)+")",
	          endX,endY);
	else 
	    g.drawString("("+d4.format(Math.cos(Math.toRadians(a))*r)+","+
		         d4.format(Math.sin(Math.toRadians(a))*r)+")",
	          endX-rLen/2,endY);
		
	
	//chord
	if (c != 0) {
	    g.setColor(Color.CYAN);
	    g.drawLine(endX,endY, midX+rLen,midY);
	
	    //midpoint on chord
	    int chordMidX= (endX+(midX+rLen)) / 2;
	    int chordMidY= (endY+midY) / 2;
	    //height h
	    g.setColor(Color.YELLOW);
	    g.drawLine(midX,midY, chordMidX,chordMidY);
	}

	//arc
	g.setColor(Color.PINK);
	g.drawArc(midX-rLen,midY-rLen,2*rLen,2*rLen, 0,(int)a);	
	
	//data on screen	
        g.setColor( Color.BLACK );
	g.drawString("area="+d4.format(Math.PI*r*r),w-200,45); 	                             
	g.drawString("circumference="+d4.format(2*Math.PI*r),w-200,60);
	if (a < 180) {
            g.setColor( Color.CYAN);
	    g.drawString("base midpoint ("+d4.format((r+Math.cos(Math.toRadians(a))*r)/2)+
	  	         ","+d4.format(Math.sin(Math.toRadians(a))*r/2)+")",w-200,75);
	}
	

    }
	
    public double chordLength(double r, double a) {
    	return Math.sqrt(2*r*r - 2*r*r*Math.cos(Math.toRadians(a)));
    }	
    	
    //height of isocelese triangle
    public double heightLength(double r, double c) {
    	return Math.sqrt(r*r - c*c/4);
    }	

   public double arcLength(double r, double a) {
    	return 2*Math.PI*r * (a/360);
    }
    
    public double triangleArea(double r, double a) {
    	return r*r/2 * Math.sin(Math.toRadians(a));
    }	
    
    public double sectorArea(double r, double a) {
    	return Math.PI*r*r * (a/360);
    }

    public double distanceFormula (double x1, double y1, double x2, double y2){
    	return Math.sqrt((x2-x1)*(x2-x1) + (y2-y1)*(y2-y1));
    }
    
    //use Newton's method to solve g=PIr^2*Alpha/360 - r^2/2*sin(Alpha2PI/360)
    //letting x=Alpha2PI/360   K=2g/r^2.   g is segmentArea
    // K=x-sin(x)
    //f(x)=K-x+sin(x)   f'(x)=-1+cos(x)
    //x(n+1)=x(n) - (K-xn+sin(xn))/(-1+cos(xn)
    //Thanks to Andy Won for this math.
    //returns alpha in degrees.   alpha=2PI/360 x
    public double NewtonsAlpha(double r, double g) {
    	double xn, xn1=1, fx;  //fakeout compiler
    	double K=2*g/(r*r);
    	xn = 1;   //initial value.  crucial choice.  implies alpha=57 (1 rad) OK?
    	fx = K - xn + Math.sin(xn);
    	int iterations=1;
    	while (Math.abs(fx) > .00001 && iterations<200) {   //no more than 200 loops?   .00001 OK?
    	    xn1 = xn - fx/(-1+Math.cos(xn));
    	    fx = K - xn1 + Math.sin(xn1);
    	    xn = xn1;
    	    iterations++;
    	}
    	//seems to work for any segmentArea between 0 and semicircleArea (alpha=180)
    	showStatus("iterations"+iterations);
    	return 180/Math.PI * xn1;
    	
    }
}